Near the cross wire end, hanging from the pipe, was a solid plug, cylindrical in section.
I will always speak of it as the current in the cross wire or wires, so that no mistake, as to its place or origin, may occur.
All being at rest the number on the scale marked by the cross wire of the telescope was 572.
As the float approaches AA1, the observer at B keeps it on the cross wire of his instrument.
B now points his instrument in the direction BF, and A keeps the float on the cross wire of his instrument.
A cross wire in the microscope tells when it is accurately abreast of the line below it.
If not, the cross wire of B was moved till it coincided with dot 0, and the number of divisions of the micrometer head noted.